| 摘要 |
PURPOSE:To reduce the thickness of a formed tunnel insulating film and avoid contamination caused by resist to obtain the high quality film stably by a method wherein a patterned silicon nitride film is formed and the thickness of the first gate oxide film is partially increased by thermal oxidation with the silicon nitride film as a mask to form a second gate oxide film. CONSTITUTION:A first gate oxide film 13 which is to be a tunnel insulating film is formed on a semiconductor substrate 11 and a patterned silicon nitride film 14' is selectively formed on it. Thermal oxidation is performed with the patterned silicon nitride film 14' as a mask and the thickness of the first gate oxide film 13 around the silicon nitride film 14' is increased to form a second gate oxide film 15. After that, for instance, the silicon nitride film 14' is removed to expose the tunnel oxide film 13 and then a polycrystalline silicon film 16 is formed by CVD and the polycrystalline silicon film 16 is doped with phosphorus 17 to make the film 16 conductive. Then, in accordance with a known manufacturing method, an EEPROM in which the gate oxide film 1 3 performs as the tunnel insulating film is formed. |
